Potassium channels are ubiquitous, being present in all living organisms. These proteins share common structural elements, which confer common functional features. In general, all K+ channels have a high selectivity for K+, and are blocked by cations of similar dimensions, such as Cs+ and Ba2+. Mutations in the pore region tend to lead to either the total loss of function or K+ selectivity. We have made mutations to one of the most highly conserved residues of the pore, glycine-143, of the inward rectifier ROMK1 (Kir1.1), and examined the resulting channel properties in the Xenopus oocyte expression system with a two-electrode voltage clamp. Mutations G143A and G143R resulted in failure to express functional channels. Co-injection of wild-type ROMK1 cRNA with these mutants led to rescue of channel function, which was different from wild-type ROMK1. In both mutants, the sensitivity to Ba2+ and Cs+ was increased, the rate of onset of block by Ba2+ was enhanced, and the selectivity to potassium was reduced. Whereas the crystallographic evidence shows that cations bind to the carbonyl backbone of the pore-lining residues, the present results indicate that the side chains of these amino acids, which face away from the pore lining, also affect permeation.
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Research Article| June 18 2001
Biophysical effects of pore mutations of ROMK1
1School of Biomedical Sciences, Department of Physiology, Worsley Medical Building, University of Leeds, Leeds LS2 9NQ, U.K.
Correspondence: Dr Sunil Bhandari, at present address Hull and East Yorkshire Hospitals NHS Trust, Department of Renal Medicine, Hull Royal Infirmary, Alderson House, Level 2, Anlaby Road, Hull HU3 2JZ, U.K. (e-mail email@example.com).
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Sunil BHANDARI, Malcolm HUNTER; Biophysical effects of pore mutations of ROMK1. Clin Sci (Lond) 1 August 2001; 101 (2): 121–130. doi: https://doi.org/10.1042/cs1010121
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